Cylindrical liner



I the explosion wave.

'CYLINDRICAL LINER Samuel S. Kistler, Salt Lake City, Utah, assignor toNorton Company, Worcester, Mass., a corporation of MassachusettsOriginalNo. 2,673,131, dated March 23, 1954, Serial No. 197,278,November 24, 1950. Application for reissue December 24, 1954, Serial No.477,601

22 Claims. (CI. 309-3) Matter enclosed in heavy brackets appears in theoriginal patent but forms no part of this reissue specification; matterprinted in italics indicates the additions made by reissue.

The invention relates to liners for cylinders such as those of internalcombustion engines and of pumps and for use as bearings for spindles andshafts. This application is a continuation in part of my copendingapplication gerial No. 23,082, filed April 24, 1948, now abandone Y Oneobject of. the invention is to provide a liner of long life. Anotherobject of the invention is to provide a liner of great resistance towear. Another object of the invention is to provide a cylinder linerwhich will very slightly wear cast iron and steel piston rings. Anotherobject of the invention is to provide a cylinder liner which will veryslightly wear piston rings or pistons made of any metal.

Another object of the invention is to provide a refractory liner.Another object of the invention to provide a-liner of some or all of theabove characteristics which is nevertheless highly resistant to crackingand spelling.

Another object is to provide a liner that 15 highly resistant to thecorrosion action of condensed moisture when the engine is cold. Anotherobject of the invention is to provide a liner of sufficient strength toresist Another object of the invention is to strengthen a liner made ofrefractory material so that it can successfully be used in internalcombustion engines.

Another object of the invention is to strengthen a liner [tmade] made ofrefractory material so that it can successfully be used in oil wellsoperating under very high pressures.

Another object of the invention is to providea cylinder liner for use asthe bearing for the journal portion of a spindle or shaft. A particularexample of the foregoing is a liner for the spindle which holds thegrinding wheel in a grinding machine.

Other objects will be in part obvious or in part pointed outhereinafter.

In the accompanying drawings illustrating four ofmanypossibleembodiments of the mechanical features of this invention.

Figures 1, 2 and 3 are axial sectional views of cylindrical linersinside of metal sleeves,

Figure 4 is an axial sectional view of a bearing for' the spindle of agrinding machine.

Referring to Figure 1, I provide a cylindrical liner 1 inside of a steelsleeve 2 having an inturned flange 3. The steel sleeve 2 is incompression against the'liner 1 both radially and axially. This may beachieved by making the sleeve 2 of slightly less inside diameter thanthe outside diameter of the liner 1, then heating the sleeve 2 quitehot, say about 500 C., and then pushing the liner 1 thereinto until itcontacts the flange 3. When the sleeve 2 cools. it exerts compressiveforce in radial directions against the liner 1 because the sleeve 2shrinks in cooling, and furthermore, the sleeve 2 shrinks in an axialdirection as well as in a radial direction and therefore the flange 3 isdrawnagainst theend of the liner 1 and exerts a compressive force on itin an axial direction. I have found that it is desirable to heat theliner 1 as well as the sleeve 2 in this operation as otherwise there isdanger that the liner 1 will be cracked by thermal shock. The liner 1,being made of ceramic material' as hereinafter glefined, does "notexpand so'much as does the sleeve 2 when each of them is heated to thesame temperature. Furthermore the sleeve 2 maybe [United States PatentO" This is of high purit A Re. 23,976 Reissues! Apr. 5, 1955 heated to ahigher temperature for example C. hotter than the liner 1 with littledanger of cracking the liner 1 when the latter is introduced into thesleeve.

The liner 1 is made of essentially crystalline material selected fromthe group consisting of aluminum oxide AlzOa, silica SiOa, magnesiumoxide MgO, and zirconium oxide ZrOz and compounds and mixtures thereof,the hard crystals in the material having a hardness greater than 1000 onthe Knoop 100 scale. These materials include crystalline alumina,mullite spinel MgO'Al2O3 and zirconia ZrOz which latter shouldpreferably have from 3% to 6% of lime CaO in solidsolution in thecrystals thereof. Thus other oxides than those above mentioned in solidsolution in the crystals are not excluded and may be beneficial as inthe case of lime in solid solution in the zirconia crystals in theamount indicated. There should be no more than 10% of all material otherthan alumina, mullite, spinel and zirconia in the liner except thathafnia, which is chemically practically indistinguishable from zirconia,is calculated as zirconia.

Alumina is the best material now known to mefor the manufacture of theliners 1 and the most satisfactory process of manufacture now known tome is the 5 EXAMPLE I There is a variety of fused alumina of highpurity, usually better than 99% A1203, which is white in color and whichin the ingot is porous and has a small percentage, well under 1%, .ofsoda NazO therein. This material when crushed very finebecomeslessentially not porous because the pores have disappeared due tothe crushing. I take a quantity of this material of a size known as 900which means that the particles have an average size of about sevenmicrons but that some of the particles are very small, down to onemicron or less and that the material is a mixture of particle sizes. Itis impossible to define the actual size of the particles but thismaterial is a commercially available material well known to the art andis sufiiciently indicated by the above description. I further provide aquantity of clay-like calciummagnesium silicate such as the mineralhectorite. Taking 98% by weight of the above mentioned crystallinealumina which is a fused alumina and 2% by weight of the hectorite, Imix them in any suitable mixer such as a kneader, or dough mixer with anadditional 8% by weight of a 2% solution of methyl cellulose in water.Then I screen the mixture through a 16 mesh screen and the material isready-for molding.

I mold this material in a rubber lined mold having a steel arbor ofcylindrical shape. The pressure is applied by hydraulic fluid againstthe outside of the rubber liner. I prefer a pressure of about 5000pounds per square inch. The pressed article is then renioved from themold and after drying is fired under cone 35 conditions. Cone 35 firingconditions can be obtained by heating to a top temperature of 1750 C.holding that temperature for three hours.

The outside surface of this liner 1 is then ground to an accuratecylindrical surface as by means of a diamond grinding wheel and theliner 1 is then inserted into the steel sleeve 2 which has been heated,as above described. Then. after the parts have cooled. the insidesurface of the liner 1 is ground [perferably] preferably with a diamondgrinding wheel to a smooth and accurate running surface. Bothcylindrical surfaces of the sleeve 2 are carefully ground, the insidebefore assembly and the [outeside] outside after assembly.

EXAMPLE n There is also available on the market a calcined but notrecrystallized alumina..,. ,nown as Bayer 'etter than'99% pure. and isthe material from which the alumina of Example I is made by fusing. inan electric furnace. This calcined alumina is made by heating aluminumhydroxide to a temperature of about 1.000 C. I take a quantity of thismaterial having low soda content to the amount of 98% by weight of theprocess alumina.

solid portions of the mix, 1% of fine calcined magnesia,

and 1% of calcium borosilicate frit. This mixture is then ball-milledwet for six hours in a porcelain lined mill with flint pebbles, driedand screened through a 40 mesh screen. The resultant powder is thenmixed with /2% of a 2% solution of methyl cellulose in water and themixture is screened through a 16 mesh screen and molded as described inExample I preferably at about 5000 pounds per square inch; The resultantpiece is-then dried and fired at cone 32 (1700 C. for three hours) afterwhich it is ground and inserted into a steel sleeve 2 as previouslydesurface is ground as speciplete circle and were not a helical crack.

circumstances the hardest material in the dust consists of quartzparticles which have a hardness of 820 on the Knoop 100 scale. Thereforeif the cylinder liners'are 1000 or harder, little abrasion will beeffected. The hardest tool steel has about the hardness of quartz and istherefore on the lower edge of the acceptable hardness range. Whenmetals are rubbed over each other, microscopic points tend to sintertogether and tear pieces out even with surfaces to cohere and tear eachother or such tendency is entirely eliminated.

During the warming up period of a motor, condensation of moisture occurson the walls of cylinders during every power stroke until the walls areat a temperature above about 140 F. In fact, it is regarded as badpractice to have the cooling water circulated in the jackets at atemperature below 140 F., which means that the walls should operate atsubstantially higher temperatures. The water condensed on the walls, inthe presence of carbon dioxide under pressure and traces of sulfurdioxide, is very corrosive and may-account for a large fraction of I theobserved cylinder wall wear. I

The substances listed above are all highly resistant to the attack ofwater under these conditions and therefore experience negligiblecorrosive wear compared to cast iron or steel. Not only do the cylinderwalls, when lined with the substances listed, not wear as rapidly ascast iron or steel walls, but a surprising result is the fact that metalpistons and metal piston rings sliding on these walls are worn very muchless than on cast iron or steel. In the case of asintered alumina liner,the piston rings and piston wore only a smallfraction as fast as whenused in cast iron or steel cylinders. The explanation appears to lieinthe reduced tendency for seizure and scoring to occur and in the factthat whereas a hard dust particle can imbed in cast iron or the softersteels and therefore serve as an abrading point for many excursions ofthe piston and rings, the dust particles being softer than the linersreferred to here cannot imbed and are swept away with the first strokeof the piston, thus producing very little abrasion of the piston andrings.

While the strength of the materials listed is not equal to that of manymetals, 1 have reduced the importance of strength by shrinking a steelsleeve onto the liner, so that all of the materials are adequatelystrong for the purpose. These hard substancesare very strong incompression but weak in tension so that by applying a compressive stresson the liner, by means of the steel sleeve, so great that at no timeduring the working cycle of the engine will any portion of the liner beunder tension, 1 take advantage of the natural physical properties ofthe liner material and have achieved complete success in avoidingbreakage. l shrink the steel sleeve onto the liner with such shrinkinterference as to put the latter under approximately 30,000 pounds persquare inch tangential compression. compressive stress may be ma'degreater or lessdepending v upon the design of a particular engine butshould beat This.

till

least 8000 pounds per square inch tangential compression.

If there were no flange 3 on the upper end of the steel sleeve the liner1 might expand axially more than the sleeve 2, due to a temperaturegradient between the liner and the sleeve when the engine isoperatingunder load. and then when the power is shut off and both parts cool theliner might not have sufficient tensile strength to draw itself togetheragain, which might result in a crack forming radially through the linerin a plane perpendicular to its'axis and approximately one-third of thedistance from the top of the liner to the bottom of the piston stroke.This crack would do no harm provided it formed a com- In the latter caseit would be possible for a piece of the liner to break out.

Referring now to Figure 2, I therefore may provide a liner in two parts4 and 5 the dividing line 6 being preferably about one-fourth toone-third of the distance from the top of the upper liner 5 to thebottom of the piston stroke. This arrangement eliminates cracking fromthe cause above noted. This liner 4, 5 is made of any of the materialshereinbefore indicated as suitable materials for the liner 1 and theparts thereof are preferably formed by sintering as in the case of theliner 1. Surrounding the liner 4, 5 is a steel sleeve 8 in compressionagainst the liner 4, 5, as above described in the ease of the steelsleeve 2 but this steel sleeve 8 need not have any inwardly extendingflange. I find that cast iron piston rings readily slide over thedividing line or junction 6 without any deleterious effects.

However, the differential expansion of the liner and sleeve can benearly prevented by the use of the flange 3 as represented in Figure land this is the preferred embodiment of my invention. Differentialexpansion between liner and sleeve is quite variable from onelinermaterial to another due to large differences in coetficient ofexpansion. For example, aluminum oxide has a coeflicient of expansion ofabout 7.5)(10 per degree centigrade while that of steel is about l2 10-It will be seen, therefore, that when heat is applied from the inside bythe combustion of gases, the liner will be heated up more than the steelsleeve and may or may not expand more than the sleeve depending upon thetemperature gradient through the walls and the coefficient of expansion.In the case of sintered aluminum oxide in a motor running at fullthrottle, the liner expandsmore than the sleeve. This statement appliesto the top'end of the liner, and conditions vary from top to bottom dueto variable exposure time of the liner to heat so that ho simple rules,can be established. However, by combination of the steel flange and aliner made of two or more sections all operating conditions can be metsuccessfully with the above materials.

Figure 3 illustrates a liner of one of the above described materials inthree parts 10, 11 and 12 divided at 13 and 14 inside of a steel sleeve15 under compression as indicated and having an inwardly extendingflange 16. For many engines, especially those having large cylinders,this construction will be preferred.

As a test of the effectiveness of the compressive stress on the liner toprevent cracking due to thermal shock, a liner of sintered aluminumoxide was assembled with a steel sleeve providing compressive stress inthe liner of 30,000 lbs/sq. in. tangentially. An oxy-gas flame from ablast lamp was directed upon a spot on the inside of the liner, but inspite of the highly concentrated and asymmetric heat no cracking occurreAn unexpected favorable behavior of the liners has been that withcontinued use the surface roughness decreases although the wear is sosmall as to be unmeasurable in 600 hours of operation at 2200 R. P. M.and full throttle.

. To illustrate the surprising reduction in wear, on the cast ironpiston rings, the data below were obtained comparing a sintcred aluminaliner with a cast iron liner in a single cylinder air cooled engineoperating at 2200 R. P. M. with full throttle, and driving adynamometer. In each case the engine was run for 400-600 hours withfrequent inspection, and the wear was calculated to an average perhours.

The second column gives the actual loss of weight by each ring on a castiron liner in 100 hours. The third column gives the loss of weight ofthe rings on an alumina liner made as above described in accordance withmy invention, as a percentage of the loss of weight on cast iron.

TABLE I Cast, Iron, Alumina, Ring grams percent Similarly, an aluminumalloy piston'showed much less wear on a sintered alumina liner accordingto this invention, but due to the deposition of carbon and thedifficulty of precise micrometer measurements the data are not asreliable and are therefore not given here. The rate of wear of cast ironcylinder walls or cast iron liners is easily measurable, but we wereunable to find any wear on the sintered alumina liner according to thisinvention in 600 hours of operation.

The preferred manner of grinding the liners is to clamp the sleeve 2, 8or 15, as the case may be, in the chuck of an internal grinding machine,and then to grind a true cylindrical surface on the inside of the liner1 or 4, 5 or l0, ll, 12 as the case may be. This may be done with asuitable internal grinding machine and a diamond grinding wheel ispreferably used. A very fine finish and accurate surface can be producedusing a vitrified bonded diamond grinding wheel, but other types ofgrinding I wheels can be used such as metal bonded or resin bondeddiamond grinding wheels and in certain cases vitrified bonded siliconcarbide wheels can be used.

Since alumina, mullite, spinel and zircona have low tensile strength, itis undesirable to subject the liner 1 etc. to high tensile stress forfear of cracking them.

Therefore, a pump liner should be put under such compression uponassembly that at the maximum pressures expectable in the pump the linerwill not be in tension. A simple and safe rule to follow in makingcylindrical liners for pumps is to make the shrink interference betweensleeve and liner at least as much as the sleeve would expand if it weresubjected to the maximum mternal pressure expectable in the pump ofcourse allowing for pressure surges such as occur 1n a pump in use.

Therefore if p is the maximum pressure, r is the internal radius of thesleeve, t is the wall thickness of the sleeve, E is the modulus ofelasticity of the metal in the sleeve and I is the shrink interferencebetween the internal diameter of the sleeve and the external diameter ofthe liner,

er s uare inch p q 1:0.0011 inch Since destructive surges can occur inliquid pumps, good practice would suggest doubling this figure.

If the liner has a thickness t, then the tangential compressive stress Sin the liner can be calculated from the equation ItEE' 2r(tE-l-TE')where E is the modulus of elasticity of the liner.

If the liner is A; inch thick and made of sintered alumina withE'=50,000,000 pounds per square inch and I=0.0022", the tangentialcompressive stressan the liner will be [l4,800]13,900 pounds per squareinch, a load easily supported.

A pressure of 1000 pounds per square inch 15 what would be required topump oil of a density of 0.9 out of a well 2560 feet deep.

Many pumps handling abrasive slurries do not have to operate againstmuch pressure. However for practical purposes it is desirable to supportthe liner by a shrink 1nterference of at least 0.0001 inch per inch ofdiameter, which in the above case would put the liner under a tangentialcompressive load of 2700 pounds per square inch.

In another embodiment the invention is a bearing for a spindle or shaft.Referring now to Figure 4, a spindle for the grinding wheel of agrinding. machine has a ournal portion 21 having a helical oil groove 22therein.

This spindle 20 is, of course, made of steel. A portion of thewheel-head 23 has a cyclindrical bore 24 in which is received a'steelsleeve 25 which is in compression against a liner 26 of essentiallycrystalline material selected from the group consisting of aluminumoxide, silica, magnesium oxide and zirconium oxide and compounds andmixtures thereof, the hard crystals in the material having a hardnessgreater than 1000 on the Knoop 100 scale. The preferred material isaluminum oxide which can be made as detil) scribed in Examples 1 and II.The sleeve 25 is shrunk onto the line 26 in the manner above described.The com pressive stress required depends upon the machine and theparticular kind of grinding operation the machine is to perform, and formany machines and many grinding operations this compressive stress neednot be great. For the journalling of shafts in a transmission system thecompressive stress might be as low as 100 pounds per square inch.However for external cylindrical grinding machines of six inch swing andlarger the compressive stress should be at least 2000 pounds per squareinch and may be greater.

Referring again to Figure 4, an oil channel 30 is shown in the wheelheadcasting 23 to which oil is conducted by a pipe 31 having a valve 32, andthe oil enters a chamber 33 from which extend passages 34 in the sleeve25 to holes 35 through the liner 26 thus to lubricate the bearingsurface of the liner 26 which has been ground as by means of a diamondgrinding wheel. The oil escapes in an axial direction into a collectingring 36 being driven thereto by the groove 22. From the ring 36 the oildrains through a passage 37 in the sleeve 25 to a chamber 38 therein andthence through a passage 39 in the wheelhead 23 to any suitable oilcollector or sump whence it is pumped back again through the pipe 31.Theholes 35 can be made with a diamond core drill.

in order that the meaning'of hardness of at least 1000 on the Knoopscale may be fully understood, I give below a tableof hardness valuesand note that "Knoop 100 scale" means determined with a Knoop machinehaving a l00 gram load. In the Knoop machine the penetration of adiamond point gives the measure of hardness.

TABLE II Molis Scale Knoop 100 Scale Materials Othoclase.

Quartz (silica). Zirconia.

Mullite.

Spine].

Topaz.

Garnet.

Zircon.

Corunclurn (alumina).

which may be the aforesaid Bayer process alumina, all' parts by weight,is placed in a porcelain-lined mill with flint pebbles and water and isball-milled until the average particle size is approximately 10 microns.The resultant ball-milled slip is then filtered and dried thus producinga cake. The cake is then mixed in a suitable mixer, such as a Simpsontype mixer, with 7% of water and 1% dextrine based on the weight of thedried cake. This mix is then molded as described in Example 1 into tubeswhich are dried and fired at a. temperature preferably between about1600 C. and 1650 C. The resultant liners are then inserted into heatedsleeves as above described to make any of the articles herein described,the two parts being ground, inside and outside, in the order and in themanner above described.

Kyanite is a natural mineral and like sillimanite and [endalusite]andalusite has the formula AlzOa.SiO2. In

EXAMPLE 1V A spinel is first produced by the fusion together ofstoichiometric proportions of magnesium oxide and aluminum oxide to formMgO. Al2O3. This is fed into-a porcelainwith Example IV.

v stresses when pumping mud at moderate pressures.

EXAMPLE v .The same procedure is followed as in the case of Example IVexcepting that twice as much alumina as necessary to form the MgO.Al2O3is used. After processing as explained in Example IV the resultant lineris a cubic crystalline spinel carrying the excess alumina in solidsolution. Liners made in accordance with this example are harder andmore wear-resistant than those made in accordance EXAMPLE VI I procure aquantity of lime stabilized zirconia as described in the copendingapplication of Archibald H. Ballard and DouglasW. Marshall Serial No.139,532 filed January 19, 1950 now Patent No. 2,535,526 granted December26, 1950. This is defined as a stabilized zirconium oxide characterizedby having a crystal structure predominantly in the cubic system and theoxide having crystallized from a fusion of zirconium oxide containingore with calcium oxide as a stabilizing agent, the quantity of calciumoxide being from 3% to 6% of the amount of ZrOz in the ore, the calciumoxide being in solid solution in the zirconium oxide crystals. Iball-mill this material in water in a steel ball-mill using steel ballsuntil its average particle is between 3 and 10 microns in diameter. Ithen treat the slurry with hydrochloric 'acid to remove the iron, washit to remove the iron saltsand dry it. I mix the resultant powder in asuitable mixer with 1% of dry dextrine and sufficient 2% solution-ofmethyl cellulose in water to make the material sufiicientlytmoist tocake slightly on compression. This material is then placed in a rubberlined mold as described in Example I and pressed into the shape of atube at a pressure about 5000 pounds per square inch, dried andfired atbetween about 1750" C. and 1800 C. The resultant liner is mounted in asteel tube under compression as previously described to make any of thearticles hereinbefore described, the interior surface of the liner beingground as in the other examples. This material is dense, relativelynonporous and very resistant to attrition.

One of the expensive features of making cylindrical liners in accordancewith this invention as above described is the requirement of grindingthe external cylindrical surface of the liner 1 or 4 and or 10, 11 and12 or 26, as the case may be. -It is important to provide good contactbetween the liner and the metal sleeve throughout the interfacial areato avoid load concentrations in small areas that might lead to cracking.Alumina, mullite, spinel and zirconia are hard materials as aboveexplained and especially in the case of alumina this grinding ispreferably done with a diamond grinding wheel which is expensive.Accordingly for certain uses I have devised other embodiments of theinvention which can be made at less expense and which for the purposesintended will readily meet'the requirements of practical use. Thesefurther embodiments of the invention are illustrated in the followingexamples.

EXAMPLE VII 7 An alumina liner 1 having an internal diameter of five andthree-quarters inches and having a quarter inch wall was to be fittedinto a steel sleeve 2 for use in pumping oil well drilling mud. Theoutside of the cylinder was coated by applyingwith a'brush aone-sixteenth inch layer of bisphenol epichlorhydrin polymer coldsetting cement. In order to prevent sagging of this viscous cementduring hardening, the liner was supported on a horizontal arbor and wasrotated on its axis for about one hour during which time the cement setto a non-sagging consistency. After twenty-four hours the cement wasvery hard and strong and was machined to an accurate cylindricalsurface. In this case it was not appropriate to heat both the liner andthe steel sleeve since the organic cement would 'be injured, so thesleeve alone was heated to 135 C. which *wassufiicient ,to permit ashrink interference great enough to protect'the liner from tensile Incases where it is desired to have a" greater shrink interference theliner can be cooled with carbon dioxide snow ill) before assembly.I'have been successful in cooling liners in thci:s manner totemperatures of the order of minus EXAMPLE VIII A liner four inches ininside diameter by ten and fiveeighths inches long by five-sixteenthsinch thick made of alumina as described in Example I was to be mountedin a bronze sleeve for pumping salt water into an oil well. The outsidesurface of the alumina liner 1 was coated with a one-quarter inch thicklayer of high alumina cement having approximately the chemical formula3CaO.5AlzOa. This coated liner was kept moist for 20 days in order topermit the cement to harden properly. The liner was then mounted in acylindrical grinding machine and ground to an outside diameter of 4.750inches using a silicon carbide grinding wheel. The inside surface of thebronze sleeve was ground to a diameter of 4.746 inches. Both the sleeveand liner were then placed in an oven and heated to a temperature of 250C. at which temperature the bronze had expanded enough more than thealumina so that the liner could readily be slipped inside of the sleeve.After cooling the bronze sleeve had shrunk upon the cement coatedalumina liner with such pressure as to support it adequately for thepurpose intended.

EXAMPLE IX Since the thermal conductivity of alumina is high and thethermal conductivity of metals is still higher I have found that asubstantial fraction of the resistance to fiow of heat from the interiorof a diesel engine equipped with my cylindrical liners to the coolingjacket thereof is due to contact resistance between the parts. I findthat this contact resistance can be greatly reduced if the contact ismetal to metal and if there is an integral coating of metal on the linermade of any of the materials herein specified. Furthermore the problemof creating a perfect cylindrical surface on the liner is therebygreatly simplified. A five and three-quarters inch diameter linerfifteen inches long and one-quarter inch thick made of .alumina asspecified in Example I was intended for use in a diesel engine.This'liner was supported horizontally in a lathe and rotated slowlywhile the outer surface was sprayed with a coating of copper to a depthof .04 inch. Spraying was done with a metal spraying gun the metal beingsupplied in the form of wire and being melted by an oxy-acetylene flame.Such apparatus is now well known in industry. A sharp cutting tool wasthen mounted on the lathe and the outer surface of the liner coated withcopper as cylindrical surface 6.275 inches in diameter. This was"assembled in the manner described in Example VIII with a steel sleevehaving an inside diameter of 6.269 inches using a temperature of 400 C.Since many metals can be sprayed, this embodiment is not limited tocopper. Furthermore a layer of metal can be formed upon the surface of aliner made out of any of the materials herein specified by coating itwith a thin film of graphite and electrodepositing the metal.

Also plastics, such as ethyl cellulose, polyethylene and vinyl acetatecan be sprayed upon the outer surface of the liner and there are other.ways of applying plastic, inorganic cements and metals upon the outersurfaces of liners made of materials herein specified.

In the preferred form of my invention the material of the liner isselected from the group consisting of crystalline alumina, mullite,spinel and zirconia. Although I prefer zirconia stabilized with from 3%to 6% of lime as this has better thermal characteristics thanunstabilized zirconia, for many uses such as for bearings unstabilizedzirconia crystallized predominaptly in the monoclinic system can beused.

The word liner has herein been used to mean the parts.

1, 4, 5, 10, 11, 12 and 26 and also, in some cases, to I metals such as,for example, brass or aluminum, de-

pending uponthe particularuse for the cylindrical liner. In any use ofthe cylindrical liner of this invention where the internal surface is arunning surface to be engaged by a reciprocating, rotating, oscillatingor vibrating metal part, the liner of the invention will last longerunder practically any conditions met with in practical use. While it iscontemplated that oil or other lubricating material will be supplied tothe running surface, the liner of the invention will longer withstanduse without oil than will a steel or bronze cylinder or bearing etc.,other conditions being equal.

In the claims the parameters of compression of 8000 and 100 are to beinterpreted in accordance with the two minimums given in thespecification as tangential compressive stress in the liner. There is nocompressive stress in the liner due to the compression against it of thesleeve except tangential compressive stress which is why compressivestress" in the specification always has the interpretation "tangentialcompressive stress whether the adjective "tangentiaf is used or not.Hence in the following claims in compression against the (or said)internal liner to the extent of at least 100 (or 8000 pounds per squareinch means that the liner is under compressive stress tangentially tothe extent of at least 100 (or 8000) pounds per square inch of its crosssection and similarly the expression in the claims in compressionagainst said exterior to the extent of at least 100 pounds per squareinch means tangential compressive stress in the liner to the extent ofat least 100 pounds per square inch of its cross section.

It will thus be seen that there has been provided by this inventioncylindrical liners for the cylinders of inter-' nal combustion enginesand of pumps and for use as bearings for spindles and shafts in whichthe various objects hereinabove set forth together with many thoroughlypractical advantages are succesfully achieved. As many possibleembodiments may be made of the above invention and as many changes mightbe made in the embodiments above set forth, it is to be understood thatall matter hereinbefore set forth or shown in the accompanying drawingis to be interpreted as illustrative and not in a limiting sense.

I claim:

1. A cylindrical liner assembly comprising an internal cylindrical linerhaving a ground internal cylindrical surface, and an externalcylindrical sleeve made of metal and in compression against saidinternal liner to the extent of at least 100 pounds per square inch,said internal liner being essentially non-porous and being made ofessentially crystalline material selected from the group consisting ofaluminum oxide, silica, magnesium oxide and zirconium oxide andcompounds and mixtures thereof, the hard crystals in the material havinga hardness greater than 1000 on the Knoop 100 scale.

2. A cylindrical liner assembly comprising an internal cylindrical linerhaving a ground internal cylindrical surface, and an externalcylindrical sleeve made of metal and in compression against saidinternal liner to the extent of at least 100 pounds per square inch,said internal liner being essentially non-porous and being made ofessentially crystalline material selected from the group consisting ofalumina, mullite, spinel and zirconia, said crystalline material havinga hardness greater than 1000 on the Knoop 100 scale and there being nomore than of all material other than said material selected from thegroup consisting of alumina, mullite, spinel and zirconia in saidinternal liner.

3. A'cylindrical liner assembly according to claim 1 in which the sleeveis in compression against the internal linear to the extent of at least8000 pounds per square '16 4. A cylindrical liner assembly according toclaim 2 in which the sleeve is in compression against the internallinear to the extent of at least 8000 pounds per square lIlC 5. Acylindrical liner assembly comprising an internal cylindrical linerhaving a ground internal cylindrical surface, and an externalcylindrical sleeve made of metal and in compression against saidinternal liner to the extent of at least 100 pounds per square inch,said internal liner being essentially non-porous and being made ofcrystalline alumina and there being no more than 10% Ff all materialother than said alumina in said internal met.

6. A cylindrical liner assembly comprising'an internal cylindrical linerhaving a ground internal cylindrical'surface, and an externalcylindrical sleeve made of metal and in compression against saidinternal liner to the extent of at least 8000 pounds per square inch,said internal liner being essentially nonporous and being made ofcrystalline alumina and there being no more than 10% of all materialother than said alumina in said internal liner.

7. A cylindrical liner assembly according to claim 1 in which the sleevehas a flange in engagement with one end of said internal liner andexerting a compressive force on it in an axial direction.

8. A cylindrical liner assembly according to claim 2 in which the sleevehas a flange in engagement with one end of said internal liner andexerting a compressive force on it in an axial direction.

9. A cylindrical liner assembly according to claim 5 in which the sleevehas a flange in engagement with one end of said internal liner andexerting a compressive force on it in an axial direction.

10. A cylindrical liner assembly according to claim 6 in which thesleeve has a flange in engagement with one end of said internal linerand exerting a compressive force on it in an axial direction.

11. A cylindrical liner assembly comprising an internal cylindricalliner having a ground internal cylindrical surface, an externalcylindrical sleeve made of metal and in compression against saidinternal liner to the extent of at least 8000 pounds per square inch,said internal liner being essentially non-porous and being made ofessentially crystalline material selected from the group consisting ofaluminum oxide, silica, magnesium oxide and zirconium oxide andcompounds and mixtures thereof, the hard crystals in the material havinga hardness greater than 1000 on the Knoop 100 scale, and an inwardlyextending flange on one end of said sleeve said flange being inengagement with one end of said internal liner and exerting acompressive force on it in an axial direction.

12. A cylindrical liner assembly comprising an internal cylindricalliner having a ground internal cylindrical surface, an externalcylindrical sleeve made of metal and in compression against saidinternal liner to the extent of at least 8000 pounds per square inch,said internal liner being essentially non-porous and being made of essentially crystalline material selected from the group con sisting ofalumina, mullite, spinel and zirconia, said crystalline material havinga hardness greater than 1000 on the Knoop 100 scale and there being nomore than 10% of all material other than said material selected from thegroup consisting of alumina, mullite, spinel and zirconia in saidinternal liner, and an inwardly extending flange on one end of saidsleeve said flange being in engagement with one end of said internalliner and exerting a compressive force on it in an axial direction.

13. A cylindrical liner assembly comprising an internal liner made ofessentially non-porous crystalline material selected from the groupconsisting of aluminum oxide. silica, magnesium oxide and zirconiumoxide and compounds and mixtures thereof, the hard crystals in thematerial [being essentially non-porous and] having a hardness greaterthan 1000 on the Knoop 100 scale, said internal liner having a groundinternal cylindrical surface, an integral exterior with an outercylindrical surface made of organic plastic material on said internalliner, and a metal sleeve outside of and in compression against saidexterior [with] to [a pressure] the extent of at lens: 100 pounds persquare inch. 4

14. A cylindrical liner assembly comprising an internal liner made ofessentially non-porous crystalline material selected from the groupconsisting of aluminum oxide. silica, magnesium oxide and zirconiumoxide and com pounds and mixtures thereof, the hard crystals in thematerial [being essentially non-porous and] having a hardness greaterthan 1000 on the Knoop 100 scale, said internal liner having a groundinternal cylindrical surface, an integral exterior with an outercylindrical surface made of mineral cement on said internal liner, and ametal sleeve outside of and in compression against said exterior [witha] to the [pressure] extent of at least 100 pounds per square inch.

15. A cylindrical liner assembly comprising an internal liner made ofessentially non-porous crystalline material selected from the groupconsisting of aluminum oxide, silica, magnesium oxide and zirconiumoxide and compounds and mixtures thereof, the hard crystals in thematerial [being essentially non-porous and] having a hardness greaterthan 1000 on the Knoop scale, said internal liner having a groundinternal cylindrical surface, an integral exterior with an outercylindrical surface made of metal on' said internal liner, and a metalsleeve outside of and'in compression against said exterior [with apressure] to the extent of at least 100 pounds per square inch.

16. A cylindrical liner assembly comprising an internal liner made ofessentially crystalline material se .lected from the group consisting ofalumina, mullite,

17. A cylindrical liner assembly comprising an internal liner made ofessentially crystalline material selected from the group consisting ofalumina. mullite,

'spineland zirconia, said crystalline material being essentiallynon-porous and having a hardness greater than 1000 on the Knoop 100scale and there being no more than of all material other than saidmaterial selected from the group consisting of alumina. mullite. spineland zirconia in said internal liner, an integral exterior with an outercylindrical surface made of mineral cement on said internal liner, and ametal sleeve out side ofv and in compression against said exterior [witha pressure] to the extent of at least 100 pounds per square inch.-

18. A cylindrical liner assembly comprising an intcrnal liner made ofessentially crystalline material selected from the, group consisting ofalumina, mullite, spinel and zironia, said crystallinematerial beingessential'y non-porous and having a hardness greater than 1000 on theKnoop 100 scale and there being no more than 10% of all material otherthan said material selected from the group consisting of alumina,mullitc. spinel andzirconia in said internal liner, an integral exteriorwith an outer cylindrical surface made of metal on said internal liner,and a metal sleeve outside of and in compression against said exterior[with a pressure] to the extent of at least 100 pounds per square inch.

19. A cylindrical liner assembly comprising an internal nae-recylindrical liner having a ground internal cylindrical surface, and anexternal cylindrical sleeve made of metal and in compression againstsaid internal liner to the extent of at least pounds per square inch,said internal liner being essentially non-porous and being made ofessentially crystalline material selected from the group consisting ofaluminum oxide, silica, magnesium oxide and zirconium oxide andcompounds and mixtures thereof, the hard crystals in the material havinga hardness greater than 1000 on the Knoop 100 scale, the liner beingsupported by a shrink interference with the sleeve of at least 0.000!inch per inch of internal diameter of the sleeve.

20. A cylindrical liner assembly comprising an internal cylindricalliner having a ground internal cylindrical surface, and an externalcylindrical sleeve made 0' metal and in compression against saidinternal liner to the extent of at least 100 pounds per square inch,said internal liner being essentially non-porous and being made ofessentially crystalline material selected from the group consisting ofalumina, nzullite, spinel and zirconia, said crystalline material havinga hardness greater than 1000 on the. Knoop I00 scale-and there being nomore than 10% of all material other than said material selected from thegroup consisting of alumina. mullite, spine! and zirconia, in saidinternal liner, the liner being supported by a shrink interference withthe sleeve of at least 0.000] inch per inch of internal diameter of thesleeve.

2]. A cylindrical liner assembly according to claim 19 in which thesleeve is in compression against the internal liner to the extent of atleast 8000 pounds per square inch.

22. A cylindrical liner assembly according to claim 20 in which thesleeve is in compression against the internal liner to the extent of atleast 8000 pounds per square inch.

References Cited inthe file of this patent or the original patent'UNITED STATES PATENTS 861,726 Howell ct a1. July 30, 1907 1,597,249Riley Aug. 24, 1926 1,831,411 Dietz Nov. 10, 1931 2,204,626 Scott June18, 1940 FOREIGN PATENTS 495,824 Great Britain Nov. 14, 1938

